The US government has approved the sale to Saudi Arabia of its advanced Terminal High-Altitude Area Defense (THAAD) missile defence system. In a statement, the State Department said yesterday that the 15 billion US dollar agreement furthered US national security and foreign policy interests. <br/><br/>The statement said this would enhance Saudi Arabia and Gulf security against Iranian and other regional threats. The Pentagon's Defense Security Co-operation Agency opined this agreement would not alter the military balance in the region.